US3078255A

US3078255A - Sulfonic acid-catalyzed condensation process

Info

Publication number: US3078255A
Application number: US858046A
Authority: US
Inventors: Ronald M Pike
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1959-12-08
Filing date: 1959-12-08
Publication date: 1963-02-19
Anticipated expiration: 1980-02-19
Also published as: GB910544A

Description

United States atent fire 7 3,078,255 SULFONIC AClD-CATALYZED CONDENSA'HGN PRUQESS Ronaid M. Pike, Chelmsford, Mass., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 8, 1959, Ser. No. 858,046 11 Claims. (Cl. Mil-46.5)

wherein R is a substituted or unsubstituted monovalent I hydrocarbon group, R is an alkyl group or a hydrogen atom and n has a value of at least one can be condensed in the presence of a catalyst (e.g. sulfuric acid or potassium silonolate) to produce a variety of useful diorgano siloxane products.

By way of illustration, it is known that those hydroxylcontaining organosilicon compounds represented by Formula 1 wherein R and R have the above-defined meanings and n has a value from 1 to 7 can be condensed to form cyclic diorganosiloxanes (i.e. diorganosiloxane trimers to heptamers) which can be separated from the reaction mixture free of most of the monofunctionad and trifunctional impurities that often contaminate the hydroxyl-containing organosilicon compounds. These pure cyclic diorganosiloxanes can then be used in conventional applications wherein monofunctional and trifunctional impurities produce deleterious eifects (e.g. in the production of gums for use in producing silicone elastomers). However, the catalysts currently employed in effecting the condensation of hydroxyl-Containing organosilicon compounds also-catalyze the equilibration of diorganosiloxanes. reactions, the reaction mixture contains 648% by weight of the desired low molecular weight cyclic diorganosiloxanes and 82-94% by weight of higher molecular weight linear diorganopolysiloxane oils or gums. The equilibrium concentration of such low molecular weight cyclic diorganosiloxanes is conventionally increased above 18% by conducting the condensation in a solvent but, upon removal of the solvent from such reaction mixtures, the

equilibrium concentration of these cyclic diorganosilox-' anes reverts to 618% byweight unless the catalyst is also removed. Alternately, yields of the desired cyclic disiloxanes are thereby caused to depolymerize continuously to maintain the equilibrium concentration of the desired cyclic diorganosiloxanes in the reaction mixture. The necessity for such distillation operations increases process costs and so constitutes an undesirable feature of such processes.

As a further illustration, it is known that those hydroxylcontaining organosilicon compounds represented'by Formula 1 wherein R and R have the above-defined meanings and n has a value of at least 8 can be condensed to form diorganopolysiloxane oils and gums that can be employed, for example, in producing silicone elastomers. However, aspointed out above, the catalysts currently employed in effecting the condensation of hydroxyl-containing organosilicon compounds also catalyze equilibration reactions andso 6-18% by weight of the desired diorganopolysiloxane oils and gums are converted to lower molecular weight When equilibrium is reached in such equilibrium 2 cyclic diorganosiloxan'es- (i.e. mostly diorganosiloxane cyclic trimers and tetramers) the desired diorgan'opolysiloxaneoils and gums are 'dimin ished and the oilsand gums are contaminated by'6- 18% by weight of the low molecular weight cyclic diorgano= siloxanes.

This invention is based on the'discovery'that certain? organic sulfonic acids catalyze'thecondensation of hydroxyl-containing' organosilicon compounds represented by Formula 1 but do not catalyze the equilibration of diorganosiloxanes to a significant extent.

containing org'anosilicon compoundsin the presence of'a catalytic amount of anar'yl' sulfonic' acid or a sulfoalka noic acid.

The condensation catalysts employed in this invention are organic sulfonic acids and, in particular, aryl sulfonic' Illustrative of the aryl sul-' fonic acids employed as catalysts in this invention'are' phenyl sulfonic acid, o-toluene sulfonic acid, m-toluene' acids and sulfoalkanoic acids.

sulfonic'acid, p-toluene' sulfonic acid and alpha naphthylene sulfonic acid. Illustrative of the sulfoalkanoic acids" employed ascatalysts in thisinvention are gamma-sulfobutyric acid, gamma-sulfopentanoic acid, delta-sulfohefi anoic acid, alpha-sulfopalmitic acid andalpha-sulfoste aric' acid. The preferred catalysts are p-toluene sulfonic acid, alpha-sulfopalmi'ticacid and 'alpha sulfos'tearic acid. The catalysts can be employed as such or in the form of" their hydrates which decompose to produce the catalyst during the condensation reaction.

The hydroxyl-containing organosilicon compounds emplayed in this invention'are represented by'Formula'lp Illustrative of the'unsubstituted monovalenthydrocarbori groups represented by R in Formula 1 are the alkyl groups-f (e.g. the methyl, ethyl and octadecyl groups), the cycloalkyl groups (e.g. the cyclohexyl and the cyclopentyl groups), the aryl groups (e.g. the phenyl, tolyl, xylyl and naphthyl groups), the'aralkyl groups (e.g. the benzyland beta-phenylethyl groups), the alkenyl groups (e.g. the

vinyl, allyl and hexenyl groups) and the cycloalkenyl' v Illustrative of the substituted monovalent hydrocarbon groups represented by R in Formula 1 are the alkyl, cycloalkyl, aryl, ,aralkyl, alkenyl and cycloalkenyl groups containing as substituents one or more halogen atoms or cyano, hydroxyl or hydro- Thesesubstituents do not reactto any significant extent during thegroups (e.g. the cyclohexenyl groups).

carbonoxy (e.g. alkoxy or aryloxy) groups.

condensation reaction. The groups represented by R in Formula 1 preferably contain from 1 to 10 carbon atoms. Illustrative of the alkyl groups represented by R in? Formula 1 are the methyl, ethyl and propyl groups. In Formula I n can represent an average value in those cases where mixtures of hydroxyl-containing organosilicon com pounds are employed.

Typical of the hydroxyl-containing organosilicon'com pounds represented by Formula 1 are those :that are'more Me R (5) Patented Feb.- 19, 1963 Consequently, the yield 'of This invention provides a process which involves condensing hydroxylamazes wherein n, p and q each have a value of at least one, and R is a methyl or an ethyl group. As used herein Me denotes the methyl group and Vi denotes the vinyl group.

The hydroxyl-containing organosilicon compounds employed in this invention can be produced by known proc esses. By one such known process, a diorganodialkoxysilane is completely hydrolyzed and partially condensed in amixture of a water and a solvent (e.g. ether), to produce a suitable hydroXy-containing reactant; or a diorganodialkoxysilane is partially hydrolyzed and partially condensed to produce a suitable alkoxyand hydroxy-containing reactant. By another such known process, a cyclic diorganosiloxane is reacted with steam at an elevated temperature and pressure to produce a suitable hydroxy-com taining reactant.

In general from 0.001 part to 20 parts by weight of the condensation catalyst per 100 parts by weight of the starting hydroXyl-containing organosilicon compounds are useful in the process of this invention. From 0.1 part to 10 parts of the catalyst per 100 parts by weight of the starting organosilicon compound are preferred. Although other than the indicated amounts of catalyst can be used, no commensurate advantage is gained thereby.

The process of this invention is advantageously conducted at a temperature from 25 C. to 170 C. However, the process is preferably conducted at a temperature from 120 C. to 150 C. Adherence to the indicated temperature ranges is generally desirable but not critical.

The process of this invention involves a condensation reaction that produces water as a by product and that can be represented by the skeletal equation:

-:SiH+H0s:it%1os i +H0 When hydroxyl-containing organosilicon compounds represented by Formula 1 wherein R is an alkyl group are employed, condensation reactions represented by the following skeletal equation can also occur to produce an alcohol as a by product:

However, in the latter case, the reaction represented by Equation 6 occurs concurrently and at a faster rate. The water or the water and alcohol produced as a by product is preferably continuously removed from the reaction mixture during the reaction by suitable means, e.g. by heating the reaction mixture at reduced pressure (preferably from 1 to 10 mm. of Hg) to the above-mentioned preferred temperatures to volatilize the water or water and alcohol.

The hydroxyl-containing organosilicon compounds and the catalyst can be dissolved in an inert liquid organic compound in which they are mutually soluble and the process of this invention can be conducted therein. Suitable liquid organic compounds are ethers (e.g. diethyl ether and n-butyl ether), aromatic hydrocarbons (e.g. xylene and toluene) and aliphatic hydrocarbons (e.g. ndecane). Amounts of these liquid organic compounds from 10 parts to 1000 parts by weight per 100 parts by weight of the starting hydroxyl-containing organosilicon compounds are useful but amounts of the liquid organic compounds from 50 parts to 200 parts by Weight per 100 parts by weight of the starting hydroxyl-containing organosilicon compounds are preferred. At the completion of the process, the liquid organic compound can be removed from the desired diorganosiloxane by any suitable means, e.g. by heating the reaction mixture to a temperature sufiiciently elevated to volatilize the liquid organic compound.

At the completion of the process of this invention the catalyst can be removed from the desired diorganosiloxane by any suitable means. By way of illustration, the sulfonic acid can be removed from the diorganopolysiloxane by washing the diorganopolysiloxane with water.

Those hydroxyl-co'ntaining organosilicon compounds 4- that are represented by Formula 1 wherein R and R have the above-defined meanings and n has a value from 1 to 7 are condensed according to the process of this invention to produce mixtures containing cyclic diorganosiloxanes having the formula:

(R SiO) (8) wherein R has the above-defined meaning and p has a value from 3 to 7 and higher molecular Weight linear diorganopolysiloxanes. When the condensation of the latter-mentioned hydroXyl-containing organosilicon compounds is conducted in the above-mentioned solvents, yields of cyclic diorganosiloxanes represented by Formula 8 as high as 40% are obtained. Owing to the fact that the catalysts employed in this invention do not catalyze the equilibration of cyclic diorganosiloxanes represented by Formula 8 to form higher molecular weight diorganopolysiloxanes, the yield of these cyclic diorganosiloxanes is not reduced by such reactions when the solvent is removed. Continuous distillation of such cyclic diorganosiloxanes from the reaction mixture is not necessary to obtain yields as high as 40%.

Those hydroxyl-containing organosilicon compounds that are represented by Formula 1 wherein R and R have the above-defined meanings and n has a value of at least eight are condensed according to the process of this invention to produce linear diorganosiloxanes having the formula:

wherein R and R have the above-defined meaning and q has an average value of at least 16. Owing to the fact that the catalysts employed in this invention do not catalyze the equilibration of such dimethylpolysiloxanes, these dimethylpolysiloxanes are produced essentially free of low molecular weight cyclic siloxanes (i.e. they contain from 0% to 3% by weight of such cyclic siloxanes).

In the production of linear diorganopolysiloxanes represented by Formula 9 according to the process of this invention, the initial product is an oil. As the process is continued the viscosity of the oil increases until, in the case of alkoxy containing hydroxyl-containing organosilicon compounds, a stable alkoxy end-blocked diorganopolysiloxane oil is produced. In the latter case, the process can be stopped at an intermediate point (e.g. by removing the catalyst) to obtain a diorganopolysiloxane oil containing both hydroxyl and alkoxy end-blocking groups. In the case of hydroxyl-containing organosilicon compounds free of alkoxy groups, the final product is a gum but the process can be stopped at an intermediate point to produce a hydroxyl end-blocked diorganopolysiloxane oil.

The diorganopolysiloxane oils produced in accordance with the process of this invention are preferably those represented by Formula 9 wherein R and R have the above-defined means and q has a value from 200 to 4000. These oils can be produced by conducting the process until the viscosity or any other conveniently measured property of the oil indicates that the desired molecular weight has been obtained and then removing the catalyst by any suitable means (e.g. by Washing the oil with water to dissolve the catalyst).

The diorganopolysiloxane gums produced in accordance with the process of this invention are preferably those represented by Formula 9 wherein R and R have the above-defined meanings and q has a value from 6000 to 15000. The gums can be produced by conducting the process until the hardness (as measured, for example, by a Miniature Penetrometer) or any other conveniently measured property indicates that the desired molecular weight has been obtained and then removing the catalyst by any suitable means (e.g. by washing the gum with water).

F 6 Those diorganopolysiloxane,oils produced in accordance withthe process of this invention that contain hydroxyl end-blocking groups undergo a gradual increase in viscosity owing to the condensation of these hydroxyl groups, especially if the oilsare exposed to elevated temperatures. These oils can be stabilized against such increases in viscosity by reacting the oils with trihydrocarbonhalosilanes (e.g. trimethylchlorosilane) in order to convert the hydroxyl groups to stable trihydrocarbonsiloxy groups as illustrated by the equation:

wherein R and R have the above-defined meanings and r has a value from 1 to 3. Such cocondensations involve reactions that can be represented by Equation 7. These cocondensations are useful in producing diorganosiloxanes containing functional groups uniformly spaced throughout the siloxane chain or at the end of the siloxane chain. By way of illustration, a hydroxyl-containing dimethylpolysiloxane can be cocondensed with methylvinyldiethoxysilane to produce a siloxane containing uniformly spaced vinyl groups according to the equation:

I no (MeQSiOMQH MeSi(O can).

Vi Vi I I 02115011 H (MegSiOh SiO (MczSiO) 20 (Mez iOMH Me Me wherein x is an integer. The siloxane so produced can be cured through the vinyl groups to produce a silicone gum. As a further illustration, hydroxyl-containing dimethylpolysiloxanes [e.g.-HO(Me SiO) H] can be cocondensed with methyltriethoxysilane to produce a siloxane containing uniformly spaced ethoxy groups which canbe hydrolyzed and condensed to convert the siloxane to a silicone resin. As another illustration, a hydroxyl-containing dimethylpolysiloxane [c.g. HO(Me SiO) H] can be. cocondensed with gammahydroxypropyldimethylethoxysilane to produce a siloxane containing gamma-hydroxylpropyl chain terminating groups.

Illustrative of the alkoxysilanes represented by Formula 11 are: methyltriethoxysilane, methylvinyldiethoxysilane, gamma-cyanopropylmethyldiethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane and gamma-hydroxypropyldimethylethoxysilane.

The diorganosiloxanes that are produced in accordance with the process of this invention are known compounds that are useful in a variety of applications. Thus the cyclic diorganosiloxanes can be converted to gums which can be used in producing silicone elastomers, the diorganopolysiloxane oils can be used as hydraulic fluids and the diorganopolysiloxane gums can be used in producing silicone elastomers.

The following examples illustrate the present invention.

Example I A mixture was formed containing 265 grams of HO(Me SiO) I-I and grams of HO(Me SiO) (MeViSiO)H The mixture was heated at 90 C. at 2.0 mm. of Hg for 0.5 hours to remove any volatile materials. Para-toluene sulfonic acid monohydrate (0.04 gram) was added to the mixture and the heating at C.Lat 2.0 mm; of Hg was continued for two hours during which time the viscosity of the mixture increased. Another 0.4 gram of the mono-. hydrate was added and the heating was continued for- 2.5 hours. Then the temperature was raised to 150 C. and the mixture was heated for two hours at 2.0 mm. of Hg to produce a gum that was soluble in chloroform and toluene.

The gum so produced grams), a silica filler (40 grams) and a peroxide curing agent (1.5 grams) were mixedand cured and then postcured to produce an elas-- tomer. Theliuear shrinkage of the elastomer during postcure was 3.4% dueto curing and thermal shrinkage For comparison purposes, a similarsilicone elastomer produced from a gum that had-been of the elastomer.

prepared by known procedures was found to undergo a 6.2% linear shrinkage when similarly postcured due to curing and thermal shrinkage of the elastomer and volatilization of low molecular weight dimethylsiloxanes.

The difference in shrinkage of the elastomers during postcure was due to the substantial absence of low molecularweight dimethylsiloxanes in the former gum (i.e.-

the gum produced by the process of this invention).

Example I] Equivalent results to those obtained in Example I are obtained when alpha-sulfostearicacid or alpha-sulfopalmitic acid is used in lieu of para-toluene sulfonic acid. as the condensation catalyst.

What is claimed is: I

1.A process for condensing organosilicon compounds represented by the formula:

f H0(s i0)..R'

wherein .R is a memberselected from the group consisting of. the unsubstituted monovalent hydrocarbon groups and; the substituted monovalent hydrocarbon groups wherein.

each substituent is a memberselected from the group of the halogen atom, and the cyano, hydroxyl, alkoxyl and aryloxy groups, R is a member selected from the group consisting of. the. alkyl groups and the hydrogen atom and'n has a value of at least one, which process comprises condensing an organosilicon compound represented by said formula in the presence of a catalytic amount ofa member selected from the group consisting of the aryl sulfonic acids and the sulfoalkanoic acids each of said acids containing no more than. 18 carbon atoms.

2. A process for condensing organosilicon compounds represented by the formula: i H0(S i0)nR' wherein R is an alkyl group and n has a value from 1 to 7 and R is a member selected from the group consisting of the alkyl groups and the hydrogen atom to produce cyclic diorganosiloxanes represented by the formula:

(R2810 3 wherein R has the above-defined meaning and p has a value from 3 to 7, which process comprises condensing an organosilicon compound represented by Formula A in the presence of a catalytic amount of an aryl sulfonic acid that contains no more than 18 carbon atoms to produce a cyclic diorganosiloxane represented by Formula B.

3. A process for condensing organosilicon compounds represented by the formula:

R Ho(dio)..R'

7 wherein R is an allryl group, n has a value of at least eight and R' is a member selected from the group consisting of the alkyl group and the hydrogen atom to produce linear diorganopolysiloxanes having the formula:

R (B) wherein R and R have the above-defined meanings and q has an average value of at least sixteen, which process comprises condensing an organosilicon compound represented by Formula A in the presence of a catalytic amount of a sulfoalkanoic acid that contains no more than 18 carbon atoms to produce a linear diorganopolysiloxane composed of groups represented by Formula B.

4. A process for condensing organosilicon compounds represented by the formula:

ltlle HO (SiO) 1111 wherein n has a value of at least eight to produce a diorganopolysiloxane gum, which process comprises heating an organosilicon compound represented by said formula to a temperature from 25 C. to 170 C. in the presence of from 0.001 part to 20 parts per 100 parts of the organosilicon compound of a toluene sulfonic acid to produce a gum.

5. A process for condensing an organosilicon compound represented by the formula:

wherein R" is a methyl group, p and q each have a value of at least one and the sum of p and q has a value of at least eight to produce a diorganopolysiloxane gum, which process comprises heating an organosilicon compound represented by said formula to a temperature from 25 C. to 170 C. in the presence of from 0.001 part to 20 parts per 100 parts of the organosiiicon compound of an alpha-sulfoalkanoic acid that contains no more than 18 carbon atoms to produce a gum.

6. A process for condensing HO(Me SiO) H wherein n has an average value of} at least eight, which comprises heating HO(Me SiO) H at a temperature from 120 C. to 150 C. and at reduced pressure in the presence of from 0.1 to parts of p-toluene sulfonic acid per 100 parts by weight of the HO(Me SiO) H to produce a dirnethylpolysiloxane gum.

7. A process for condensing HO(Me SiO) H wherein n has an average value of at least eight, which comprises heating HO(Me SiO) I-I at a temperature from 120 C. to 150 C. and at reduced pressure in the presence of from 0.1 to 10 parts of alpha-sulfostearic acid per parts by weight of the HO(Me SiO) I-I to produce a dimethylpolysiloxane gum.

8. A process for condensing HO(Me SiO) H wherein n has an average value 013 at least eight, which comprises heating HO(Me SiO) H at a temperature from C. to C. and at reduced pressure in the presence of from 0.1 to 10 parts of alpha-sulfopalmitic acid per 100 parts by weight of the HO(Me SiO) I-I to produce a dimethylpolysiloxane gum.

9. A process which comprises cocondensing (1) an organosilicon compound represented by the formula:

wherein R is a member selected from the group consisting the unsubtituted monovalent hydrocarbon groups and the substituted monovalent hydrocarbon groups wherein each substituent is a member selected from the group consisting of the halogen atoms and the hydroxyl, cyano, alkoxy and aryloxy groups, R is a member selected from the group consisting of the alkyl groups and the hydrogen atom and n has a value of at least eight and (2) and allcoxysilane represented by the formula:

I K lb-r wherein R and R have the above-defined meanings and r has a value from 1 to 3, said cocondensation being etfected in the presence of a catalytic amount of a member selected from the group consisting of the aryl sulfonic acids and the sulfoalkanoic acids each of said acids containing no more than 18 carbon atoms.

10. The process of claim 9 wherein the alkoxysilane is methyltriethoxysilane.

11. The process of claim 9 wherein the alkoxysilane is methylvinyldiethoxysilane.

References Cited in the file of this patent UNITED STATES PATENTS 2,371,068 Rochow Mar. 6, 1945 2,843,555 Berridge July 15, 1958 2,916,507 erschner et a1 Dec. 8, 1959 FOREIGN PATENTS 570,580 Canada Feb. 10, 1959

Claims

1. A PROCESS FOR CONDENSING ORGANOSILICON COMPOUNDS REPRESENTED BY THE FORMULA: